Four sewage sludge(SS)feedstocks with distinct properties were converted into biochars by pyrolysis at 300−700℃,in order to clarify the effects of the composition difference of SS feedstocks.The yields of biochars pr...Four sewage sludge(SS)feedstocks with distinct properties were converted into biochars by pyrolysis at 300−700℃,in order to clarify the effects of the composition difference of SS feedstocks.The yields of biochars present a positive correlation with the contents of ash in SS.Notedly,the contents of organic matter(OM)in SS largely determine the quality of biochars.SS feedstocks with high content of OM are more likely to form stable biochars with higher aromaticity/carbonization degree,and the formed biochars possess higher calorific values.The contents of residual OM in biochars derived from SS feedstocks with low content of OM likely fail to meet the needs of soil improvement(10 wt.%).Most of heavy metals(HMs)existing in raw SS are remained in biochars after pyrolysis.The biochar produced from SS feedstocks with high content of HMs usually contains higher contents of HMs.Surprisingly,the leachability of HMs in biochars is all weakened to some extent compared to raw SS.In addition,the biochars show higher thermal stability and pH values,and P/K nutrients are enriched in biochars.The biochars prepared from four SS feedstocks exhibit different adsorption ability of methylene blue,especially at low dosage of biochar.展开更多
Liquefaction of sewage sludge(SS)in ethanol-water cosolvents is a promising process for the preparation of bio-oil/biochar products.Effect of the combined use of ethanol and water on the distribution/transformation be...Liquefaction of sewage sludge(SS)in ethanol-water cosolvents is a promising process for the preparation of bio-oil/biochar products.Effect of the combined use of ethanol and water on the distribution/transformation behaviors of heavy metals(HMs)contained in raw SS is a key issue on the safety and cleanness of above liquefaction process,which is explored in this study.The results show that pure ethanol facilitates the migration of HMs into biochar products.Pure water yields lower percentages of HMs in mobile/bioavailable speciation.Compared with sole solvent treatment,ethanol-water cosolvent causes a random/average effect on the distribution/transformation behaviors of HMs.After liquefaction of SS in pure water,the contamination degree of HMs is mitigated from high level(25.8(contamination factor))in raw SS to considerable grade(13.4)in biochar and the ecological risk is mitigated from moderate risk(164.5(risk index))to low risk(78.8).Liquefaction of SS in pure ethanol makes no difference to the pollution characteristics of HMs.The combined use of ethanol and water presents similar immobilization effects on HMs to pure water treatment.The contamination factor and risk index of HMs in biochars obtained in ethanol-water cosolvent treatment are 13.1-14.6(considerable grade)and 79.3-101.0(low risk),respectively.In order to further control the pollution of HMs,it is preferentially suggested to improve the liquefaction process of SS in ethanol-water mixed solvents by introducing conventional lignocellulosic/algal biomass,also known as co-liquefaction treatment.展开更多
基金Project(21707056)supported by the National Natural Science Foundation of ChinaProject(20192BAB203019)supported by the Natural Science Foundation of Jiangxi Province,China。
文摘Four sewage sludge(SS)feedstocks with distinct properties were converted into biochars by pyrolysis at 300−700℃,in order to clarify the effects of the composition difference of SS feedstocks.The yields of biochars present a positive correlation with the contents of ash in SS.Notedly,the contents of organic matter(OM)in SS largely determine the quality of biochars.SS feedstocks with high content of OM are more likely to form stable biochars with higher aromaticity/carbonization degree,and the formed biochars possess higher calorific values.The contents of residual OM in biochars derived from SS feedstocks with low content of OM likely fail to meet the needs of soil improvement(10 wt.%).Most of heavy metals(HMs)existing in raw SS are remained in biochars after pyrolysis.The biochar produced from SS feedstocks with high content of HMs usually contains higher contents of HMs.Surprisingly,the leachability of HMs in biochars is all weakened to some extent compared to raw SS.In addition,the biochars show higher thermal stability and pH values,and P/K nutrients are enriched in biochars.The biochars prepared from four SS feedstocks exhibit different adsorption ability of methylene blue,especially at low dosage of biochar.
基金Project(21707056) supported by the National Natural Science Foundation of ChinaProject(20151BAB213024) supported by the Natural Science Foundation of Jiangxi Province,ChinaProject(GJJ14302) supported by the Scientific Research Fund of Jiangxi Provincial Education Department,China
文摘Liquefaction of sewage sludge(SS)in ethanol-water cosolvents is a promising process for the preparation of bio-oil/biochar products.Effect of the combined use of ethanol and water on the distribution/transformation behaviors of heavy metals(HMs)contained in raw SS is a key issue on the safety and cleanness of above liquefaction process,which is explored in this study.The results show that pure ethanol facilitates the migration of HMs into biochar products.Pure water yields lower percentages of HMs in mobile/bioavailable speciation.Compared with sole solvent treatment,ethanol-water cosolvent causes a random/average effect on the distribution/transformation behaviors of HMs.After liquefaction of SS in pure water,the contamination degree of HMs is mitigated from high level(25.8(contamination factor))in raw SS to considerable grade(13.4)in biochar and the ecological risk is mitigated from moderate risk(164.5(risk index))to low risk(78.8).Liquefaction of SS in pure ethanol makes no difference to the pollution characteristics of HMs.The combined use of ethanol and water presents similar immobilization effects on HMs to pure water treatment.The contamination factor and risk index of HMs in biochars obtained in ethanol-water cosolvent treatment are 13.1-14.6(considerable grade)and 79.3-101.0(low risk),respectively.In order to further control the pollution of HMs,it is preferentially suggested to improve the liquefaction process of SS in ethanol-water mixed solvents by introducing conventional lignocellulosic/algal biomass,also known as co-liquefaction treatment.
